I used a wet vac to remove the water from the dishwasher. remove cover and filter/strainer from bottom of dishwasher. remove screw which allows you to lift the plastic piece to access check valve. Original check valve looked like new , I installed new check valve re installed parts . Job done and issue resolved .
Went to on line video and followed it. The old gasket came right out and the new one fit right in. Started at the top middle and worked the gasket in on both sides to make sure it was evenly spaced.
To perform the repair, the door panel must be removed (8 Torx screws) and the door removed from the hinges in order to access the lower door seal. For this model Bosch and other similar models, the hinge springs must then be disengaged (safer) or kept from retracting. To disengage the springs requires removing the entire unit, disconnecting the water supply, and flipping it on its side to disengage the springs. I chose the latter, keeping the unit in place, holding the hinges with vice-grips on either side, then removing the door. This was not easy and caution is required. Either method is risky with a 20-year dishwasher. The replacement part does not fit as well as the original (much sturdier) part, but appears to seal well for now. Repair videos on the internet are for different, newer models where disabling the hinges as described here is not required, making the repair much easier. Recommend looking carefully at your model/manual to determine if the difficulty of the repair is easy or hard.